Don't purge resources for trivial GrContext flushes

src/gpu/GrContext.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrContext.h"
 #include "GrContextPriv.h"
 #include "GrContextOptions.h"
@@ skipping 210 matching lines @@
     // drawPath on SkGpuDevice
     GrContext* context = reinterpret_cast<GrContext*>(data);
     context->flush();
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 
 void GrContext::flush(int flagsBitfield) {
     ASSERT_SINGLE_OWNER
     RETURN_IF_ABANDONED
-
+    bool flushed = false;
     if (kDiscard_FlushBit & flagsBitfield) {
         fDrawingManager->reset();
     } else {
-        fDrawingManager->flush();
+        flushed = fDrawingManager->flush();
     }
-    fResourceCache->notifyFlushOccurred();
+    if (flushed) {
+        fResourceCache->notifyFlushOccurred();
+    }
     fFlushToReduceCacheSize = false;
 }
 
 bool sw_convert_to_premul(GrPixelConfig srcConfig, int width, int height, size_t inRowBytes,
                           const void* inPixels, size_t outRowBytes, void* outPixels) {
     SkSrcPixelInfo srcPI;
     if (!GrPixelConfigToColorType(srcConfig, &srcPI.fColorType)) {
         return false;
     }
     srcPI.fAlphaType = kUnpremul_SkAlphaType;
@@ skipping 547 matching lines @@
     ASSERT_SINGLE_OWNER
     fResourceCache->setLimits(maxTextures, maxTextureBytes);
 }
 
 //////////////////////////////////////////////////////////////////////////////
 
 void GrContext::dumpMemoryStatistics(SkTraceMemoryDump* traceMemoryDump) const {
     ASSERT_SINGLE_OWNER
     fResourceCache->dumpMemoryStatistics(traceMemoryDump);
 }